Difference between revisions of "Mistral/DSL"

Revision as of 13:58, 28 January 2014

Mistral DSL specification

Version 0.1

Main objects

• Service
• Action
• Workflow
• Task
• Event

Service

Provides some specific functionality. For example, Nova service provides functionality for VMs management in OpenStack.

Attributes

• name - string without space, mandatory attribute
• type - currently we support the following types: RESTAPI, OPENSTACKSERVICE, OSLO_RPC, this is a mandatory attribute
• parameters - dictionary depending on type of the service, this parameter can be optional. For example for REST API it should contain url of the service, method of authentication etc.
• actions - list of actions provided by this service

YAML example:

 Service:
    name: Nova
    type: REST_API
    parameters:
        key:value
    actions:
        create-vm:
          ......
        delete-vm:  
          .....

Action

A function provided by services. For example Nova service provides the following actions: create-vm, shutdown-vm

Attributes

• name - string without space, mandatory attribute
• parameters - dictionary, which structured is defined by service type. For REST service it contains url and method.
• task-parameters - dictionary containing parameters which should or could be specified in task

YAML example:

 create-vm:
     parameters:
         url: servers
     task-parameters:
         name:
           optional: False

Workflow

Attributes

• name - string without space, mandatory attribute
• tasks - list of task in this workflow, each task represent some step in worflow
• events - list of events in workflow, e.g. timer or periodic events

YAML example:

 Workflow:
    tasks:
       create-vms:
         .....
       attache-volumes: 
         .....

Task

Represents a step in workflow, for example attaching volume

Attributes

• name - string without space, mandatory attribute
• action - name of action to perform
• dependsOn - list of tasks which should be execute before this tasks, this is optional parameter
• parameters - list of parameters

YAML example:

 create-vms:
    action: Nova:create-vm
    parameters:
       image_id: 1234
       flavor_id: 42

Events

By event it is possible to invoke specific task.

Attributes

• name - string without space, mandatory attribute
• type - can be PERIODIC, TIMER, CEILOMETER_ALARM
• tasks - list of tasks which should be execute on event
• parameters - list of parameters, defined by task

YAML example:

 backup-vm:
    type: periodic
    tasks: [create_backup, delete_old_backup] 
    parameters:
       time: 1 0 * * *

Full YAML example:

 Workflow:
 tasks:
   runJob:
     requires:
       createVM: $.vm_ip != null
     action: DemoApp:runJob
     on-success: deleteVM
     on-error: sendJobError
 
   deleteVM:
     action: Nova:deleteVM
     on-finish: end
 
   sendJobError:
     action: std:email
     parameters:
       address: admin@mycompany.com
       subject: Workflow error
       body: Error occurred while running a VM job in execution {$.execution.id}
     on-finish: deleteVM
 
 # Creating a VM and waiting till it is up (an IP address has been assigned).
 
   createVM:
     action: Nova:createVM
     on-success: waitForIP
     on-error: sendCreateVMError
 
   waitForIP:
     action: std:repeat
     parameters:
       task: getIP
       retries: 5
       delay: 3000
       break-on: $.vm_ip != null
     on-finish:
       sendCreateVMError: $.vm_ip = null
     on-error:
       sendCreateVMError 
 
   getIP:
     action: Nova:getIP
 
   sendCreateVMError:
     action: std:email
     parameters:
       address: admin@mycompany.com
       subject: Workflow error
       body: Failed to create a VM in execution {$.execution.id}
     on-finish: end
 
 # Terminal no-op task.
 
   end:
     action: Util:no-op
 
 events:
   runJob:
     type: periodic
     tasks: runJob
     parameters:
       cron-pattern: "*/1 * * * *"
 
 Services:
   Nova:
     type: REST_API
     parameters:
       baseUrl: {$.novaURL}
     actions:
       createVM:
         parameters:
           url: /servers/{$.vm_id}
           method: POST
         response:
           select: $.server.id
           store-as: vm_id
       getIP:
         parameters:
           url: /servers/{$.vm_id}
           method: GET
         response:
           select: $.server.accessIPv4
           store-as: vm_ip 
       deleteVM:
         parameters:
           url: /servers/{$.vm_id}
           method: DELETE
 
 DemoAPP:
   type: MISTRAL_REST_API
   parameters:
     baseUrl: http://{$.vm_ip}:8080/
   actions:
     runJob:
       parameters:
         url: /runJob
         method: GET

Initial execution context

 {
   "novaURL": TBD,
   "imageID": TBD
 }

When a workflow starts Mistral also adds execution information into the context so the context looks like the following:

 {
   "novaURL": TBD,
   "imageID": TBD,
   "execution": {
     "id": "234234",
     "workbook_name" : "my_workbook",
     "project_id": "ghfgsdfasdfasdf"
     "auth_token": "sdfljsdfsdf-234234234",
     "trust_id": "oiretoilkjsdfglkjsdfglkjsdfg"
   }
 }